In the field of matrix printers it is of course well known that a printer may include one or more print heads which are caused to be moved in a reciprocating manner across the printer for printing in serial manner. The print head may be moved by a cable and pulley arrangement, a lead screw, or a cam drive or like drive mechanism. Each of the print heads includes a plurality of elements supported in group-like manner and actuated or energized at high speed to cause printing of dots by movement of dot-making elements including droplets of ink or print wires attached to solenoids and caused to be impacted against the paper. The print wires or ink jet nozzles are usually closely spaced in vertical manner so as to print the dots making up the characters in a line as the print heads are moved across the printer. In this manner, a line of printed characters is completed upon travel of the print head in one direction across the paper.
Another form of matrix printer includes the use of a plurality of printing elements supported from a carriage in a manner wherein the elements are aligned horizontally across the printer and upon each pass of the carriage respective dots of characters are printed in a line or row and subsequent passes of the carriage and printing elements cause additional lines of dots to be printed to complete the dot matrix characters along the line of printing. Common arrangements include the use of four or eight printing elements supported from the carriage.
A timing strip with slots or like indicia is commonly used to originate the actuation of the printing elements wherein one or more sensors sense the slots or other indicia to print dots in precise columns across the paper. While the printing has usually been performed in one direction, for example, left to right, it is more recently that printing has been done in both directions of travel of the print head carriage or of the printing element carriage.
Representative or typical prior art dealing with a device for feeding a print head is shown in U.S. Pat. No. 3,858,702 issued to N. Azuma on Jan. 7, 1975 wherein printing is performed in the left to right direction and non-contact switches positioned at right and left ends of the printer and operable with a shutter make up limit switches which change state for reversal of direction of the print head.
U.S. Pat. No. 3,858,703 issued to H. Duley on Jan. 7, 1975 discloses a bi-directional dual head printer which uses a registration strip with a plurality of equally-spaced narrow transparent slots and wherein each print head prints a portion of the line of characters in a mode of printing wherein every other line is printed as the print heads move from left to right and printing the interspersed lines as the print heads move from right to left.
U.S. Pat. No. 3,970,183 issued to P. Robinson et al. on July 20, 1976 shows a printer capable of printing in either forward or reverse direction and monitoring is performed by detecting both the direction of head movement and print head position at any time during the operation. The information is detected by a pair of optical channels and a registration strip has displaced sets of transparent slots therein.